Giant Meateating Bats

I love tempting diversions. Not long after arriving in Tucson and setting up a pollen lab, I read news stories about a cable built across the Grand Canyon to a guano mine. On the Hualapai reservation at Quartermaster View, a few miles upstream from Rampart Cave, huge buckets suspended by the cable transported guano from Bat Cave across the canyon to fill trucks on the south side ("Treasure of Granite Gorge," Time, September 23, 1957). A New York Times headline on the story read, in part, "Big Vacuum Cleaner to Be Used to Mine Deposit Left by Giant, Meat-Eating Bats Millions of Years Ago" (March 27, 1957).

The headline is a hoot. I suppose that free-tailed bats (Tadarida brasiliensis) can be called meat eaters, since they eat insects. However, giants they are not, even among bats, nor was this vast guano deposit likely to be millions of years old. Nevertheless, the cave sounded interesting. The ground sloth skeleton exhibited at Yale's Peabody Museum, which was found at Aden Crater, New Mexico (together with long toenails, hair on a patch of skin over the rump, and dung balls) had been buried in bat guano (Lull 1930). Maybe Bat Cave sheltered its own ground sloth carcass. Furthermore, might bat guano not be as rich in fossil pollen as was ground sloth dung? Who knew what trophies might be found in desert caves, caves as dry as the tombs of the pharaohs? I simply had to see this operation for myself.

I admit that the Colorado River lacks pyramids, a sphinx, and a Valley of the Kings and Queens. But for all its archaeological treasures, even Egypt does not have perishable remains of any extinct animals as extraordinary and mysterious as the Shasta ground sloth. If not as hot and dry as Egypt, the lower Colorado River area is sufficiently arid to preserve a few remarkable mummies of its own. "Never mind the gold and buried treasure," I might have said, had I prayed to Ra, the Sun God, who has the head of a hawk and wears the solar disc as a crown. "I ask only for a previously unknown and undiscovered cave of layered sloth dung, with mummified ground sloth remains!"

In June 1958, geochronologist Bernie Arms and I followed a maze of dirt roads from Kingman, Arizona, to Quartermaster View, a splendid overlook into Grand Canyon. We parked near the tall cable tower and walked to the rim. Suddenly, there it all was, an amazing vista down to a tiny brown strip far below, with white streaks marking rapids in the muddy Colorado. The sagging cable faded from view. At 9,010 feet in length and 1.5 inches in diameter, this was reportedly the longest commercial cable in the world. U.S. Steel had reportedly spent $689,000 to manufacture it ("Treasure of Granite Gorge," Time, September 23, 1957). The expense seemed justified by the size of the deposit—an estimated 100,000 tons of guano (New York Times, March 27, 1957) expected to yield, according to the U.S. Guano Corporation's optimistic projection, a profit of $12.5 million.

The engineer in charge, Bill Freiday, arranged for us to cross the canyon the next day. When the time came, I assumed an indifference that I did not feel and followed Bernie into a head-height steel bucket, engineered to hold a load of

3,500 pounds. We swung out across the canyon, an adrenalin rush accompanying the giddy descent, and eventually landed on the north side of the Colorado, one mile away and 3,650 vertical feet below the rim, passing only one tower in between. Then there was a short cable car run, on what seemed like a sled, up to the huge mouth of the cave itself.

The miners seemed pleased to find someone, even greenhorn academics, interested in what they were doing. U.S. Guano Corporation chemist Varley Crompton had previously written me, "We occasionally run across bat 'grave yards' which are heaps of skulls and bones, sometimes up to four or five feet in diameter" (personal correspondence, March 17, 1958). The miners confirmed that there were plenty of bat bones and showed us mummified free-tailed bat carcasses. But they reported nothing large, nothing like a giant meat-eating bat, and certainly no big bones of ground sloths or other large animals.

We collected guano samples near the mouth of the cave and farther in, beyond an active bat colony, in a large, totally dark interior room filled with odorless dry fossil guano the texture of face powder. Our sample from a depth of just over 7 feet later yielded a date of 12,900 ± 1,500 radiocarbon years; the large error margin indicated that the sample contained too little organic carbon to yield a more precise measurement. Although we did not find any fossils of extinct animals, the deposits might well have been old enough to contain them; perhaps, under the unexcavated guano pile, they lie there still. The samples also contained no fossil pollen, though they did contain scales of small moths and fragments of beetle exoskeletons.

Exciting as the trip had been, Bat Cave was, for our purposes, a washout. Nevertheless, I was sure that once word of our interest in cave deposits began to spread, someone in the region would pass on news of previously unknown or unappreciated ground sloth caves like Rampart Cave. I had to wait twenty years, however, before Ra finally delivered, letting me join a team studying the dung and diet of the largest extinct mammalian megaherbivore known in Arizona.

Not long after our visit to Bat Cave, I learned that a military jet from a base in Nevada, apparently hot-dogging illegally within Grand Canyon air space, had nicked the cable. It was ruled unsafe. The U.S. Guano Corporation recovered its investment from the government and did not rebuild. I am told that the Huala-pai tribe presently operates a casino at Quartermaster View, with clients ferried in from Las Vegas by helicopter.

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